Latching mechanism for an extensible antenna



Aug. 23, 1966 D. L. HOLZSCHUH ETAL 3, 67,6 5

LATCHING MECHANISM FOR AN EXTEN5IBLE ANTENNA Filed May 16, 1963 5Sheets-Sheet l 3/ 3g I 4/ /4- V I l 35 I ,///4 5 FIG 2 v INVENTORSDonald L. Holzschuh James L. Seymour Jr:

Allan Van Horne 8" 1966 D. L. HOLZSCHUH ETAL 3,267,625

LATCHING MECHANISM FOR AN EXTENSIBLE ANTENNA Filed May 16, 1963 5Sheets-Sheet 2 INVENTORS Donald L. Holzschuh James L. Seymour Jr AllanVan Horne BY Wk 5 M 4 z Agents 1966 D. HOLZSCHUH ETAL 3,267,625

LATCHING MECHANISM FOR AN EXTENSIBLE ANTENNA Filed May 16, 1963 5$heets-$heet 5 44\%| & 43

4 INVENTORS Donald L. Ho/zschuh James L. Seymour Jr. Allan Van Horne BYM Agents United States Patent 3,267,625 LATCHIN G MECHANISM FOR ANEXTENSIBLE ANTENNA Donald L. Holzschuh and Allan Van Horne, Richardson,and James L. Seymour, .lr., Mesquite, Tex., assignors to Collins RadioCompany, Cedar Rapids, Iowa, a corporation of Iowa Filed May 16, 1963,Ser. No. 280,831 Claims. '(Cl. 52111) This invention pertains toextensible and retractable telescopic radio antennas and moreparticularly to latching devices that ensure extension and retraction inthe order of arrangement of sections.

The latching mechanisms of this invention are utilized with antennasthat have power erecting systems to pull upward on the respectiveinnermost unextended telescopic tubular sections. Telescopic antennas ofthis type are to be extended in their order of arrangement of sectionsfrom the innermost sections to the outermost sections. As each sectionis fully extended, an upper stop and lower supporting stop becomeeffective to retain the extended section fixed relative to an adjacentouter section so that both the unextended adjacent outer section and thefully extended inner section can be forced upward together.

When the retarding force of friction between two adjacent sections isless than the weight of the outer one of the sections, latching means isobviously not required to hold the outer section down until the innersection is fully extended. In practice the inner section that is beingraised may develop sufiicient friction to cause the outer section torise prior to engagement of the supporting stop and cause the innersection to fall. The excessive friction is most likely to develop whenthe antenna is being erected in high wind.

According to this invention, each tubular section of an antenna, exceptthe innermost section, has an upper fastening collar that has hingedlatches for engaging corresponding notches in an upper adjacent collarof an inner section, a release pin for each latch that may be forcedoutwardly to release the latch, a band or sleeve about each tubularsection, each band engaging the release pins of the collar within whichit is being guided in response to the respective section being fullyextended to release the latches that are holding downwardly on thesection adjacent to the section that has just been raised, each of thesections to be extended having a notch within the band or sleeve to beengaged by corresponding stop balls, and plunger and spring meansoperated in response to separation of the unlatched collars to positionsaid balls inwardly into the corresponding notches to prevent downwardmovement of the extended sections.

An object of this invention is to provide relaible cooperating latchingmechanisms for both retracted and extended positions of each section toensure inner to outer sequence of positioning of sections duringerection and outer to inner sequence of positioning of sections duringretraction.

The description and the appended claims may be more readily understoodby reference to the accompanying drawings in which:

FIG. 1 is a side view of a four-section telescopic antenna mounting asrepresentative of larger structures, a portion of one of therepresentative intermediate collars being cut away to show latchingmechanisms;

FIG. 2 shows a cross section of two adjacent telescopic sections attheir guide rings to show the method of keying against rotation;

FIG. 3 is a side view of a mounting of an intermediate section withinouter sections of a telescopic antenna when 3,267,625 Patented August23, 1966 the innermost sections have been extended, the intermediatesection being shown just as it is started to be pulled upward from forceexerted on the innermost sections by traction rollers (not shown); and

FIG. 4 is a cross section view of a collar between two extended sectionsto show a ball locking mechanism.

In FIG. 1 an upper, extended, innermost section 10 is shown supportedwithin an adjacent section 11 to which an upper fastening collar 12 isattached. Likewise, section 11 is telescoped within section 14 to whicha fastening collar 13 is attached. Section 14 is mounted within anoutermost section that has a fastening collar 15. This outermost sectionis telescoped within the base 16 that supports the antenna. The latches17, 18, and 19 retain the outermost section and sections 14 and 11respec- I tively in a retracted position until they are to be extendedin order from the innermost section to the outermost section. Eachcollar has a release pin such as pin 20 that is mounted in collar 13.Each release pin is actuated by a band or a sleeve similar to sleeve 21of section 11 shown in FIGS. 3 and 4. When section 11 is fully extended,the sleeve 21 has engaged the pin 20 and has released the latch 18 thatis mounted to the lower adjacent collar 15.

Each collar also has a ball stop that is to be actuated by a spring andplunger. In FIG. 1 the plunger 22 is forced upward in opposition to itsspring by its lower edge being in contact with the upper face of theadjacent collar 15. With the plunger in this position, the stop ball 23is in an outward position relative to section 11 to permit the upperbeveled portion of sleeve 21 to pass upward to a position above the ballas shown in FIG. 3. As a section 11 is lifted, the spring for forcingthe plunger 22 downward forces the ball 23 into a notch on sleeve 21 asshown in FIG. 4 to prevent subsequent retraction of the section 11 untilafter the adjacent outer section 14 has been returned to its normaltelescoped position.

In detail, each tubular antenna section except the innermost section 10has a fastening and stop collar attached to its upper end. Obviously, acollar is not required for the section 10 because it is always the firstsection to be extended and is always under control of a power tractiondevice that is not shown. Other than the collars becoming progressivelylarger for the outer sections, the collars are similar. The uppermostcollar 12 that is attached to the section 11, next to the innermostsection, requires no latch. In a preferred embodiment each collar is analuminum casting that has two diametrically spaced hold down latches toprevent premature extension and two diametrically spaced ball stops thatprevent premature retraction.

As clearly shown in FIG. 4, each collar has a lower annular lip portion24 that is fitted into a rabbet formed within the upper edge of theinner wall of the tubular antenna section 14. The lip 24 of the collaris permanently attached within the rabbet. The inside cylindrical wallof the collar 13 has a slightly greater diameter than the aluminum stopsleeve 21 of the section 11 that is to be guided within the collar. Thestop sleeve 21 is permanently attached to the outer wall of the aluminumtelescopic antenna section 11 to provide a firm stop for locating thesection 11 in an extended position. The stop sleeve also functions as acam or a control surface for positioning hold-down latch 18 and stopball 23.

A notch for receiving a stop ball is located in the vertical outer wallof the sleeve 21 at a point adjacent to the location of the stop ball 23when the antenna section 11 is fully extended. The upper edge of thenotch is slanted upwardly and outwardly from the bottom of the notch toapply force outwardly on the ball 23 when the section 11 tends to movedownwardly as the upward traca tion is decreased. Although a preferredembodiment is shown using a relatively long sleeve 21, a bandcorresponding to only the top portion of the sleeve that extends abovethe top of the notch 26 may be used. The bottom of the band would have abeveled lower edge to correspond to the upper edge of the notch 26.

A cylindrical upper bearing 27 as shown in FIG. 3 lines the upperportion of the cylindrical inner wall of the collar 13. A bearing thatfunctions very satisfactorily comprises two similar semicircular bandsretained by a coil spring retainer 29. A circumferential groove that hasan annular cross section for receiving the spring retainer 29, is formedby a groove in the outer surface of the bearing 27 and also a similarmating groove in the inside wall of the collar 13. The bearing piecesare preferably fabricated from a plastic material that has good wearingqualities. The inside diameter of the hearing 27 is slightly larger thanthe diameter of the antenna section 11 to provide a sliding fit. Thelower edge 28 of the bearing 27 is beveled so that its surface contactssubstantially all the surface of the beveled upper edge of the sleeve 21to provide a stop that limits the upward motion of the section 11relative to section 14.

The latch 18 of FIG. 1 is rotatably mounted on a horizontal bearing pin35 that is fitted Within the U shaped bracket 30 cast into the upperouter edge of the lower adjacent collar 15. A torsion spring 31 thatencircles the bearing 35 and has its ends attached to the latch 18 andthe collar 15, urges the latch inwardly to bear against the wall of thecollar 13. The spring is more clearly shown with reference to latch 12that is attached to collar 13 in that the bracket for latch 19 has beencut away to show the spring 32 that urges latch 19 inwardly. A notch orseat 34 in the retaining plate 25 that is mounted by screw 36 in theouter wall of collar 13 is located to receive the tooth 33 of the latch18 so that when a release pin 20 is free to move to its inward position,the tooth bears against the upper edge of the notch as the collar tendsto travel upwardly prematurely. The cylindrical release pin 29 is asliding fit in a bore that extends inwardly from the bottom of the notch34 through the vertical wall of the collar 13. The pin 20 is heldcaptive by the antenna section 11 at one end, and by the retaining plateat the other. The diameter of the outer end of the pin 20 has a smallerdiameter than that of most of the pin so that it may extend through ahole in the plate 25 to contact the inner surface of the tooth 33. Thelength of the pin 20 is such that it extends between the wall of theantenna section 11 and the surface of the tooth 33 when the tooth isseated in the notch 34.

The stop as shown in FIG. 4 for retaining the antenna section 11 in anextended position comprises a steel ball 23, a positioning controlplunger 22, and a notch 26 in the wall of the sleeve 21. The ball iscontained within the hole that is located radially through an innerportion of the wall of the collar 13 at a position opposite that of thestop notch 26 during full extension of the antenna section 11. Theplunger 22 is slidingly mounted vertically within a cylindrical holethat intersects the hole for ball 23. The ball 23 is also a sliding fitwithin its mounting hole. The'transverse distance between the surface ofthe plunger when it is in its lower position and the outer wall of theantenna section 11, not including the sleeve 21, is slightly greaterthan the diameter of the stop ball 23. As the ball is positionedinwardly toward the antenna section 11 by the plunger 22 it functions asa stop between the upper lip of notch 26 (FIG. 4) and the lower edge ofits mounting hole. The vertical hole for the plunger 22 is drilledthrough the wall of the collar 13. As shown in FIG. 1, the plunger 22 isurged downwardly by the helical spring 37 that is mounted between thetop of the plunger and a retaining cover 38 that is secured over the topof the mounting hole.

The distance of downward travel of the plunger 22, while the collar 13is spaced above its adjacent lower collar 15, is restricted by a pin orscrew 39 that is fastened radially through the outer wall of the collar13 so that its inner end fits within a slot 40 within the outer surfaceof the plunger 22. The upper portion of the plunger 22 is cylindricalbut the lower portion has a vertical section milled off to provide aflat surface 41 such that the stop ball 23 may be moved outwardly. Theupper surface 42 of the flat surface 4-1 is gradually tapered so as tofunction as a cam against the surface of the ball. When adjacent collarsare positioned together, the upper surface of the lower collar pressesagainst the lower end of the milled portion of the plunger to press theplunger up wardly into its collar in opposition to the downward force ofthe spring 37 to permit the milled portion to be raised high enough toaccommodate outward movement of the ball 23. Then, when the ball 23 iscontacted by the sleeve 21, it is forced outwardly so that it does notprotrude within the inner Wall of the collar to prevent passage of thesleeve.

With reference to FIGS. 2 and 4, the bearing for guiding the lower endof the antenna section 11 comprises two semicircular bands 43 and 44that are similar to the semicircular bands comprising the upper bearing27.

These pieces are also fabricated from a plastic or other good bearingmaterial. The thickness of these pieces corresponds to the thickness ofthe bearing 27. These bearings, however, are firmly attached to theinner section 11 by countersunk screws and travel within the antennasection 14. The pieces of hearing are actually a little shorter thanfull semicircles so that diametric gaps 45 and 46 exist between the endsof the semicircular bearing pieces. Each of the aluminum antennasections is extruded with diametrical, longitudinal tongues or keys 47and 48 that travel within the gaps 45 and 46 respectively that areprovided between the bearing pieces 43 and 44. Since all of the sections(except the innermost section) are provided with keys corresponding tokeys 47 and 48, all the sections are restrained from rotation so thatthe collars are always aligned and the latches can engage thecorresponding notches or seats.

Frequently, in erecting an antenna, roller traction systems areutilized. The rollers first start to raise the innermost section 10. Thelatches 17, 18, and 19 in FIG. 1 secure all sections to the base exceptthe innermost section 10. Whensection 10 is fully extended, its sleeve,that corresponds to the sleeve 21 of FIG. 3, engages the pin 49 torelease the latch 19. As section 11 begins to be lifted upwardly thestop ball in the collar 12, that corresponds to the stop ball 23 ofcollar 13, is forced inwardly by the corresponding spring and plunger toposition the ball within the stop slot of the section 10. As the rollerscontinue to operate, they pass over the collar 12. When the rollers nolonger provide an upward force on the section 1%, the stop ball, that issimilar to ball 23, becomes effective to prevent retraction of thesection 10. Likewise, the section 11 continues to be extended until thesleeve 21, as shown in FIG. 3, forces the pin 20 outwardly to releasethe latch 18. As the collar 13 starts to be separated from the adjacentcollar 15, the stop plunger 22 is forced downwardly by springpressure toposition the stop ball 23 in the stop slot 26 of the sleeve 21 (FIG. 4).In the same manner andin successive order, sections 11 and 14 and thenlastly the outermost section are fully extended. The traction rollersare always effective to control the position of the antenna; and whenthey are not erecting or retracting the antenna, they are operating asbrakes to maintain the antenna in an erected position. When the antennais to be retracted, the rollers are reversed in direction of rotationand the outermost section is retracted into the base first. All otherinner sections are retained in a locked position until the collar 15 isreturned to the base and the corresponding stop plunger is forcedupwardly so that the stop ball may be forced out of its stop notch bydownward movement of the section 14 that is adjacent to the outermostsection.

Obviously, the order of retraction continues from the outermost sectionto the innermost section until all of the sections are retracted. Theoperation of the hold down latches and the stop ball mechanism preventseither extension or retraction out of order because of binding, andthereby prevents any section from falling and damaging the antennasystem.

Although this invention has been described with respect to a particularembodiment thereof, it is not to be so limited, as changes andmodifications may be made therein which are within the spirit and scopeof the invention as defined by the appended claims.

What is claimed is:

1. In an extensible antenna having a plurality of telescopic tubularsections that are to be extended in an inner to outer sequence and to beretracted in an outer to inner sequence, the combination of a hold-downlatch and a supporting stop for each of said sections to controlsequence of extension and retraction, said latch and said stop for anyof said sections being mounted on the periphery of the upper end of thatsection, a latch seat for each section in alignment with said latch ofan adjacent section, means for urging each of said latches inwardly toengage a respective one of said seats in the immediate adjacent innerone of said sections thereby to prevent separation of said adjacentsections, a release pin extending inwardly from each of said latches tothe outer surface of the adjacent inner one of said sections, means forurging said supporting stop of any one of said sections inwardly inresponse to the extension of that section from its fully telescopedposition relative to its adjacent outer section, each of said tubularsections having an outer control surface near its lower end comprising aprotruding upward facing ledge and a protruding downward facing ledge,said upward facing ledge being in vertical alignment with said releasepin of the adjacent outer one of said sections, said downward facingledge being in vertical alignment with said supporting stop of the sameadjacent outer one of said sections, said upward facing ledge of any ofsaid sections in response to substantially full extension thereofengaging said release pin of that one of said sections immediatelyadjacent to the outer surface of said extended section to force therespective one of said latches outwardly for unlatching said immediatelyadjacent outer section from the next adjacent outer section, thereby topermit extension of said immediately adjacent outer section, saidsupporting stop that is mounted on said immediately adjacent outersection being operated inwardly in response to upward movement of thisimmediately adjacent outer section to engage said downwardly facingledge of said fully extended section to fasten said extended section tosaid immediately adjacent outer section, said supporting stop beingoperated outwardly in response to subsequent full retraction of saidimmediately adjacent outer section to release said extended section forpermitting its retraction, and said respective release pin being forcedinwardly in response to downward movement of said extended section tocause said respective latch to engage its seat for latching togethersaid immediately adjacent outer section and said next adjacent outersection.

2. A telescopic antenna having a plurality of telescopic tubularsections with sequence control means for governing the order ofextension and the order of retraction of said sections, said sequencecontrol means comprising a collar secured to the upper edge of each ofsaid tubular sections, each of said sections that are telescopicallymounted within the outermost one of said sections being a sliding fitwithin the collar of its adjacent outer section, each of said sectionsthat are mounted within said outermost section having a stop sleeveabout its lower end, each of said collars having an upper portion with asmaller inside diameter than that of its lower portion so that the upperportion has a slightly smaller inside diameter than the outside diameterof adjacent inner ones of said sleeves to prevent its passage while saidlower portion has sufficiently large inside diameter to accept saidadjacent sleeve, the lower inside ledge of said upper portion of saidcollar engaging the upper edge of said adjacent sleeve to provide anupward stop as said section with said adjacent sleeve is fully extendedupwardly, each of said collars that has an upper immediately adjacentone of said sections having a latch with a tooth for engaging saidcollar of said upper immediately adjacent section and spring means forurging the tooth of said latch inwardly against the outer surface ofsaid upper adjacent collar, each of said collars having a notch alignedvertically with the tooth of the lower adjacent ones of said latches toreceive said lower adjacent tooth when the adjacent sections are fullyretracted, thereby to fasten said adjacent collars together, a releasepin for each latch slidingly mounted radially with reference to saidsections to extend from the bottom of said notch that receives saidlatch to the outer surface of the adjacent inner one of said tubularsections, the upper portion of said sleeve of said adjacent sectioncontacting the inner end of the respective one of said release pins whensaid inner section is substantially fully extended as determined by saidrespective upward stop, said sleeve of said adjacent inner sectionforcing said release pin outwardly in response to said adjacent sectionbeing fully extended to release the adjacent latch, thereby to permitextension of said section with said outwardly positioned release pin.

3. In a telescopic antenna according to claim 2, a stop mounted in eachof said collars, a control link for each of said stops extending betweeneach of said stops and the lower surface of its collar, means for urgingeach of said stops inward and its respective link downward, said stopsin their inward positions engaging said sleeves about said sectionsmounted within said respective collars, said stops engaging said sleeveto support said respective sections within adjacent sections, saidcontrol links extending below the lower surfaces of their respectivecollars while said respective stops are engaging said sleeves, each ofsaid control links being operated by engagement with the upper portionof said lower adjacent collar in response to said adjacent collarscoming together because of re traction of respective sections, and eachof said stops in response to operation of said respective control linksmoving outwardly to release said respective sections being supportedthereby.

4. In a power-driven telescopic antenna, a plurality of tubulartelescopic sections, a fastening collar fixed coaxially to the top endof all of said sections except the innermost one, each of said sectionshaving a stop sleeve fixed circumferentially near its lower end, each ofsaid collars having an inside wall with upper and lower coaxialcylindrical portions separated by a ledge, each of said ledges beingengageable with the one of said sleeves that encircles said one of saidsections that is being guided within said collar to provide a limit stopwith respect to extension of that section, said upper cylindricalportion of each collar having the required inside diameter to provide asliding fit for that inner one of said sections being guided thereby,said lower cylindrical portion of each collar having a greater insidediameter than that of the corresponding one of said upper cylindricalportions to receive loosely said stop sleeve of its inner guidedsection, a latch rotatively mounted to each of said collars except thatcollar of the next to the innermost one of said sections, each of saidlatches having a tooth for pressing inwardly against the outer wall ofthe upper adjacent collar as the adjacent sections are telescopedtogether, spring means for urging said tooth inwardly, a notch in eachof said outer walls in line with said latch of the adjacent lower one ofsaid collars to be engaged by the tooth thereof, each of said notchesbeing opposite the space to be occupied by said stop band of an inneradjacent one of said sections when it is extended to its upper limit, alatch release pin positioned radially within the wall of each 'of saidcollars, said pin for each collar being mounted slidingly to extendbetween said space in said lower portion of said corresponding wall andthat position in said notch for receiving said corresponding tooth, eachof said release pins being pressed inwardly by said tooth that is beingurged inwardly within said notch, and each of said stop sleeves inresponse to its section being fully extended as determined by said limitstop engaging the inner end of the adjacent one of said release pins toforce the adjacent one of said teeth from the corresponding notch,thereby to unlatch adjacent collars for extension of said sections inorder from said innermost section to said outermost section as thesections are forced upward.

5. In a telescopic antenna as claimed in claim 4, a stop ball mounted inan opening within the vertical wall of each of said collars, a slidingplunger for each ball mounted vertically in the Wall of said respectivecollar to contact the surface of said ball that is facing outwardrelative to the one of said telescoping antenna sections that is beingguided within the respective collar, each of said plungers beingoperated upwardly relative to its respective ball in response to thelower surface of the plunger contacting the upper surface of the outeradjacent one of said antenna sections when the adjacent sections aretelescoped together, the face of each of said plungers that is incontact with said corresponding ball while said plunger is operatedupwardly being recessed to permit said corresponding ball to be forcedoutwardly by said respective guided antenna section so that said sleeveof said section that is being guided within the collar can move freelypast said ball, means for forcing each of said plungers downwardly inresponse to separation of the said collars of the said telescopedsections, each of said plungers during its downward travel functioningas a cam to force said respective ball inwardly so that it protrudesbeyond the inner surface of said collar within which it is mounted tocontact a downwardly facing ledge of said sleeve of said guidedrespective section while it is fully extended to prevent retraction ofsaid extended section until the adjacent outer section is fullyretracted.

References Cited by the Examiner V UNITED STATES PATENTS RICHARD 'W.COOKE, 3a., Primary Exmmner

1. IN EXTENSIBLE ANTENNA HAVING A PLURALITY OF TELESCOPIC TUBULARSECTIONS THAT ARE TO BE EXTENDED IN AN INNER TO OUTER SEQUENCE AND TO BERETRACTED IN A OUTER TO INNER SEQUENCE, THE COMBINATION OF A HOLD-DOWNLATCH AND A SUPPORTING STOP FOR EACH OF SAID SECTIONS TO CONTROLSEQUENCE OF EXTENSION AND RETRACTION, SAID LATCH AND SAID STOP FOR ANYOF SAID SECTIONS BEING MOUNTED ON THE PERIPHERY OF THE UPPER END OF THATSECTION, A LATCH SEAT FOR EACH SECTION IN ALIGNMENT WITH SAID LATCH OFAN ADJACENT SECTION, MEANS FOR URGING EACH OF SAID LATCHES INWARDLY TOENGAGE A RESPECTIVE ONE OF SAID SEATS IN THE IMMEDIATE ADJACENT INNERONE OF SAID SECTIONS THEREBY TO PREVENT SEPARATION OF SAID ADJACENTSECTIONS, A RELEASE PIN EXTENDING INWARDLY FROM EACH OF SAID LATCHES TOTHE OUTER SURFACE OF THE ADJACENT INNER ONE OF SAID SECTIONS, MEANS FORURGING SAID SUPPORTING STOP OF ANY ONE OF SAID SECTIONS INWARDLY INRESPONSE TO THE EXTENSION OF THAT SECTION FROM ITS FULLY TELESCOPEDPOSITION RELATIVE TO ITS ADJACENT OUTER SECTION, EACH OF SAID TUBULARSECTIONS HAVING AN OUTER CONTROL SURFACE NEAR ITS LOWER END COMPRISING APROTRUDING UPWARD FACING LEDGE AND A PROTRUDING DOWNWARD FACING LEDGE,SAID UPWARD FACING LEDGE BEING IN VERTICAL ALIGNMENT WITH SAID RELEASEIN OF THE ADJACENT OUTER ONE OF SAID SECTIONS, SAID DOWNWARD FACINGLEDGE BEING IN VERTICAL ALIGNMENT WITH SAID SUPPORTING STOP OF THE SAMEADJACENT OUTER ONE OF SAID SECTIONS, SAID UPWARD FACING LEDGE OF ANY OFSAID SECTIONS IN RESPONSE TO SUBSTANTIALLY FULL EXTENSION THEREOFENGAGING SAID RELEASE PIN OF THAT ONE OF SAID SECTIONS IMMEDIATELYADJACENT TO THE OUTER SURFACE OF SAID EXTENDED SECTION TO FORCE THERESPECTIVE ONE OF SAID LATCHES OUTWARDLY FOR UNLATCHING SAID IMMEDIATELYADJACENT OUTER SECTION FROM THE NEXT ADJACENT OUTER SECTION, THEREBY TOPERMIT EXTENSION OF SAID IMMEDIATELY ADJACENT OUTER SECTION, SAIDSUPPORTING STOP THAT IS MOUNTED ON SAID IMMEDIATELY ADJACENT OUTERSECTION BEING OPERATED INWARDLY IN RESPONSE TO UPWARD MOVEMENT OF THISIMMEDIATELY ADJACENT OUTER SECTION TO ENGAGE SAID DOWNWARDLY FACINGLEDGE OF SAID FULLY EXTENDED SECTION TO FASTEN SAID EXTENDED SECTION TOSAID IMMEDIATELY ADJACENT OUTER SECTION, SAID SUPPORTING STOP BEINGOPERATED OUTWARDLY IN RESPONSE TO SUBSEQUENT FULL RETRACTION OF SAIDIMMEDIATELY ADJACENT OUTER SECTION TO RELEASE SAID EXTENDED SECTION FORPERMITTING ITS RETRACTION, AND SAID RESPECTIVE RELEASE PIN BEING FORCEDINWARDLY IN RESPONSE TO DOWNWARD MOVEMENT OF SAID EXTENDED SECTION TOCAUSE SAID RESPECTIVE LATCH TO ENGAGE ITS SEAT FOR LATCHING TOGETHERSAID IMMEDIATELY ADJACENT OUTER SECTION AND SAID NEXT ADJACENT OUTERSECTION.